The goal of these studies is an in-depth investigation of the thymus-derived lymphocyte (T cell). Murine T-cell clones and hybrids will be used as homogeneous sources of antigen-specific activities and lymphokines. Lymphokines are mediators of T-cell function and participate in delayed hypersensitivity and immunity to tumors, viral, and fungal diseases. Lymphokines to be studied include lymphotoxin (LT), migration inhibitory factor (MIF), interferon (IFN), and T-cell growth factor (IL2). Antigen-specific activities will include induction of replication and lymphokine production in T-cell clones. Conditions that regulate induction of lymphokines will be studied by determining the nature of the H2 restricting element in antigen-specific induction of LT production. Lymphotoxin messenger RNA will be isolated from T-cell clones and hybrids by immunological precipitation of polyribosomes with a monoclonal anti-LT antibody. Alternatively, polyadenylated RNA will be isolated and enriched for LT mRNA by size fractionation. In vitro translates (frog oocytes, rabbit reticulocytes, or wheat germ extract) will be assayed for LT, MIF, IFN, and IL2. LT cDNA probes will be prepared by taking advantage of the fact that a T-cell clone is induced to make 2000-fold more LT after induction with a T-cell mitogen. Cloning will be accomplished after purification of LT mRNA, cDNA preparation and insertion into pBR322 or pcDV1, and replication in E. coli. cDNA clones will be identified by hybridization selection with LT mRNA, by differential hybridization of cDNA probes prepared from mRNA of induced and uninduced T-cell clones, or by subtraction of common cDNA sequences by cascade hybridization. Genomic LT DNA probes will also be used to screen cDNA libraries. The LT gene will be transfected with a mammalian expression vector into fibroblasts or T cells by means of protoplast fusion, and its expression studied. Organization of T-cell genes will be studied with the LT cDNA probe and an additional T-cell probe for an antigen-binding protein from a T-cell hybrid. Genes for LT and other T-cell products will be mapped by somatic cell hybridization. These studies will provide basic information on the nature of genetic regulation of lymphokines and will provide information on the interrelationships of lymphokines with each other and with T-cell antigen receptors. (IS)